In previous air brake system, it was common practice to employ apparatus as illustrated and described in FIG. 1 of Japanese Patent (Tokuko) No. 45-6082 and in FIG. 1 of Japanese Patent (Tokukai) No. 59-50850. A example of such prior art systems is illustrated in FIG. 3 of the present application in which the following is a detailed description of the components and operation thereof. It will be seen that FIG. 3 shows a system in which the brake valve BV is in the release position and the brake cylinder BC is exhausted. In the release position, the control line CP is exhausted by the brake valve BV so that the pressure is at atmosphere. Under such a condition, the electropneumatic master controller 100 moves the rod 102 to the left due to the added force of the return spring 101. Thus, the release contact 103 switches to a closed position while at the same time the contact 104 switches to an open position. When the release contact 103 is closed, the release command line RS is connected to the power source line and the release solenoid valve RMV is energized and is opened so that the straight air line SAP is exhausted to atmospheric pressure. In addition, since the braking contact 104 is opened, the brake command line BS is disconnected from the power source line, and the brake solenoid valve BMV is deenergized and is closed. Thus, the straight air line SAP is not connected to the main air reservoir line MRP. Therefore, the relay valve RV closes the air supply, and at the same time the intermediate exhaust valve rod moves downward so that the brake cylinder BC is exhausted to atmosphere. In viewing FIG. 3, it will be seen that the check valve CV1 is arranged in such a manner that the blocking direction is from the straight air line SAP. It will be noted that the throttle valve NV is connected in parallel to the check valve CV1. The air reservoir AR which supplies the air to the brake cylinder BC through the relay valve RV and the check valve CV2 in which the free flow direction is toward the air reservoir AR. The output or the exhaust outlet EX relay valve RV is connected to atmosphere.
Let us assume that the brake system is in the released state, as is illustrated in FIG. 3, and that it is desired to move the handle of the brake valve BV into an appropriate braking position. Thus, the control line CP will be pressurized a given amount which is dictated by the selected brake position so that the rod 102 is urged toward the right against the force of the return spring 101, as viewed in FIG. 3. This causes the release contact 103 to open so that the releasing solenoid valve RMV is deenergized and the exhaust port EX is closed. Accordingly, the straight air line SAP is disconnected from the atmosphere. Now as the rod 102 moves further to the right, it causes the compression of the buffer spring 105, and in turn causes the closing of the braking contact 104. Therefore, the brake solenoid valve BMV is energized so that it becomes open and the compressed air pressure in the main air reservoir line MRP is conveyed to the straight air line SAP. The exhaust valve rod of relay valve RV moves upward to unseat and open the air supply valve. Thus, the compressed air pressure in the air reservoir AR is fed into the brake cylinder BC so that a brake force is applied to the wheel of the railway car. In addition, when the rod 102 of controller 110 is pushed back slightly to the left due to the pressure in the straight air line SAP and the pushing forces of the two sides, an equilibrium is reached on the right and left sides of the rod 102. Thus, the braking contact 104 will be opened so that the brake soleoid valve BMV is deenergized and its valve is reseated. Thus, the straight air line SAP is no longer pressurized by the main pressure reservoir line MRP. At this time, the release contact 103 also remains opened. Therefore, the straight air pipe or line SAP is neither pressurized nor exhausted so that the system is in a lapped condition.
In this lapped condition, if the brake valve BV is moved to a lesser or lower notch, or position of braking, the control line CP will be exhausted to a certain degree depending on the particular selected brake position. Thus, the rod 102 will move to the left and the release contact 103 will close. This causes the release solenoid valve RMV to be energized which results in the unseating and opening of the air portion of the valve. Since the straight air line SAP is exhausted, the rod 102 will again move to the right and the release contact 103 will open. Thus, the opening of release contact 103 causes the deenergization and closing of release solenoid valve RMV. Thus, the exhausting of the straight air line SAP is stopped and the system assumes the same lapped condition as described above. At the same time, as a result of the movement of the relay valve RV, the brake cylinder BC is also exhausted to a certain degree, depending on the above-mentioned brake position. After this, when the brake valve BV is moved into the release position, each of the structural parts are again returned to the release position, as shown in FIG. 3.
It will be appreciated that there are various types of electropneumatic master controllers in operations of the prior art besides the system shown and disclosed in the present application. However, they are all basically the same.
The electropneumatic master controllers are generally designed so that the pressure to the straight air line SAP is introduced via the throttle valve NV to protect it from transient effects during the pressurization. Thus, any water vapor contained in the compressed air condenses due to adiabatic expansion at the throttle valve NV during its introduction. Therefore, the inside of the diaphragm plate chamber can sometimes become frozen in winter, thereby causing defective operation and/or complete failure. Although FIG. 3 is drawn simply for purposes of explanation, a great many electropneumatic master controllers of the prior art are almost entirely composed of mechanical components which results in a highly complicated mechanical design so that it is necessary to make great many checks and adjustments in order to achieve troubleless operation.